<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8">
    <link rel="stylesheet" href="../common/reset.css">
    <title>块级居中</title>
    <style>
        .box {
            width: 200px;
            height: 200px;
            background-color: aquamarine;
            margin: 0 auto;
        }
    </style>
</head>

<body>
    <div class="box"></div>
</body>

</html>